This invention relates to an actuator and more particularly to a hybrid piezoelectric-magnetostrictive rotary or linear actuator.
Many devices require rotary (or linear) motion on a lightweight platform. An example includes actuators for antenna stabilization and pointing platforms. Existing antenna stabilization and pointing systems are commonly based on servomotors, stepper motors, or less commonly, on piezoelectric actuators. See, “Inertial Solutions” February, 2004, http://www.inertialsolutions.us/products_servo_control.htm; “HSG2320 Lightweight Bi-axis Gimbal Actuator,” February, 2004, http://www.starsys.com/products/electromagneticactuators/biaxisassemblies/product.asp?ID=HS G2320; and “Orbiter GNC & C, Subsystem weekly update,” February, 2004,
http://www.estec.esa.nl/conferences/esmats99. Most of these prior art systems are 1-or 2-axis systems.
A single-axis rotary motor using magnetostrictive and piezoelectric materials to create an electrical resonance circuit has been built. See, R. Venkataraman, “A Hybrid Actuator,” M. S. thesis, University of Maryland, 1995. The motor design was optimized for use as a helicopter flaperon. A linear motor has also been built using the same concept. See, B. Clephas and H. Janocha, “New Linear Motor With Hybrid Actuator,” in Proceedings SPIE 3041, 1997, pp. 316-325.
Airex Corporation of Dover, N.H. has developed a spherical motor-bearing system that is advertised for high-accuracy pointing systems. This is a five degree-of-freedom system (two rotational and three translational) and is intended to carry heavy payloads. See, “Magnetic Bearings,” February, 2004, http://www.airex.com/products/magnetic.htm.
Many of the existing antenna pointing and stabilization systems are too heavy, take up too much space, and/or require too much power for the small unmanned aerial vehicles (UAVS) on which they would be installed. In the motor described by Venkataraman cited above, a piezoelectric stack clamps a mask to a disc while a magnetostrictive rod pushes the mass tangential to the disc. This configuration relies on friction to advance the disc to provide rotary motion. This motor is single-axis only. Because this motor relies on friction, large forces cannot be transmitted.
The Airex magnetic bearing mentioned above is one of a class of “electronic gimbals” that many believe will eventually replace mechanical gimbals. Such electronic gimbals, however, are generally bulky and are well suited for high payload requirements but are not a good solution for small and micro-UAVs.